The invention relates to an image recording apparatus for recording an image on a sheet while transporting the sheet on a sheet transport path.
In electrophotographic image recording apparatus, a sheet is fed from a sheet feeding tray to an image recording section where an image is formed on the sheet. Then the sheet is output to a sheet output tray. A sheet may become jammed on its way on a sheet transport path. A sheet jam is likely to occur particularly in the image recording section. This is because a sheet tends to be curled while undergoing various processes in the image recording section, such as a developer-image transfer process performed by a transfer device or a fusing process performed by a fusing device.
A sheet jam is also likely to occur in a reversing transport path on which, in duplex image formation (an image is formed on both sides of a sheet), a sheet with an image formed on a first side is reversed and transported back to the image recording section. This is because the duplex image formation involves a sheet passing through many bifurcations of the sheet transport path.
In the event of a sheet jam, image recording apparatus suspend an image forming process until all sheets present on the sheet transport path are removed. JP H09-134050A discloses that a sheet jammed in the image recording section is removed by drawing the image recording section in a forward direction out of the image recording apparatus and opening a side wall or the like of the section to expose the sheet transport path.
The foregoing configuration of the prior art apparatus, however, involves a small level of exposure of a portion of the sheet transport path located in the image recoding section, even with the image recording section drawn out and the side wall opened. Thus, this configuration renders it hard for a user to remove a jammed sheet. In particular, recent image recording apparatus with high functionality have a complex configuration that renders it hard to provide a large space for removing a jammed sheet.
In consecutive image formation that involves a plurality of sheets present on the sheet transport path, a user is necessitated, if only a small level of exposure of sheet transport path is available, to open side walls or the like of different portions of the image recording section in order to check if all the sheets are removed from the sheet transport path.
As a solution to the foregoing problem, image recording apparatus has been proposed that includes a movable first unit and a movable second unit. In the first unit, a first path as part of a sheet transport path is positioned. The first unit is movable along a first direction toward front of the apparatus, to be drawn out of the apparatus. With the first unit drawn out of the apparatus, the second unit is movable along a second direction, perpendicular to the first direction, to be drawn out of the first unit. In the second unit, a second path as another part of the sheet transport path is positioned.
The proposed apparatus eliminate the need for a dedicated space for drawing the second unit out of the first unit along the second direction, since existing space for removing a printed sheet also serves as the space for drawing the unit 2 out of the unit 1. Also, the proposed apparatus allow the second unit to be detached from the first unit by being drawn out of the first unit, thereby enabling the first and second paths to have a greater exposed area than in conventional apparatus where the first and second units are integrated in a single unit.
In the first unit, further, a fusing device is located along the first path. The fusing device has: a heat roller for fusing a toner image formed on a sheet; and a pressure roller, pressed against the heat roller, for applying pressure to the sheet. When the first unit is drawn out of the apparatus, part of the exterior of the fusing device is exposed. The fusing device also has sheet removers positioned in contact with respective circumferential surfaces of the heat and pressure rollers.
Additionally, the entire fusing device is covered with a covering under which components such as described above are fixedly positioned. The covering is provided because the components of the fusing device are hot due to the heat of the heat roller, compared with components of the other devices. The covering prevents the other devices from overheating, and also serves to maintain the circumferential surface of the heat roller at a constant temperature.
The configuration of the proposed apparatus, however, makes it difficult for a user to remove a sheet jammed in the fusing device, and all the more difficult because of the heat of the fusing device. In recent image recording apparatus that feature high-speed printing capabilities, it is impossible to stop rotation of transport rollers quickly in the event of a sheet jam, and a jammed sheet is transported forward until the transport rollers come to a stop. Thus, a jammed sheet sometimes becomes entangled in between the heat roller and the pressure roller, even when the sheet jam occurs in a location other than the fusing device. Therefore, it is important to make it easier to remove a sheet jammed in the fusing device.
A possible solution is to allow a contact member, such as a sheet remover, that is placed in contact with the circumferential surface of the heat roller to be detached from the circumferential surface as necessary so that the circumferential surface is exposed. However, the proposed image recording apparatus requires two steps to move the contact member: first, draw the second unit out of the first unit to make space for the contact member to move; and only then, move the contact member.
A feature of the invention is to provide an image recording apparatus that facilitates removal of a sheet jammed in a fusing device positioned in a first unit.